Gwyneth Paltrow has provoked the wrath of the dietetic establishment by saying that she avoids feeding her children bread, rice and pasta, because she believes that these carbohydrate foods aren't good for them. Paltrow was writing in her new low-carb, gluten-free cookbook, It's All Good, which is out in April, and whose recipes are said by her publisher to "form the basis of the diet Gwyneth goes back to when she's been overindulging, when she needs to rebuild, or lose weight."

Dieticians who subscribe uncritically to government nutritional guidelines have been wheeled out to testify to how 'vital' carbohydrate is in the diet, and warn in the bleakest terms of the dangers of restricting it. Paltrow is putting her children, aged eight and six, "at risk of nutrient deficiencies", warns one. Her children "won't be able to think straight as their brain won't be functioning", says another. In the same Daily Mail piece, it is even observed that Paltrow's children are thin – shock horror! – as if this was automatically cause for concern. So accustomed are we to the sight of overweight children, thin ones are beginning to look unusual.

Casting Paltrow in the role of the neurotic celeb, selfishly inflicting her own faddy and dangerous eating habits on her poor starved offspring, has undeniable appeal, especially for those of us who aren't rich or pretty and who struggle daily with our own excess weight. The New York Post says: "The book reads like the manifesto to some sort of creepy healthy-girl sorority." But Paltrow has a point: no one, not even a child, actually "needs" to eat carbs.

Of course, the processed food industry works ceaselessly to convince us that we must eat highly refined starchy foods, such as breakfast cereals and white bread, trumpeting that they give us energy. But all food gives us energy. Contrary to what we have been led to believe, there is no dietary "need" to eat starchy carbohydrates at all.

Now if Paltrow was to starve her children of protein, then social workers could quite legitimately come knocking at her door. We are made of protein. Our bodies require it to build and repair muscles and tissue. But we have no absolute requirement for carbohydrate.

It is only in recent times that starchy foods have been presented as health foods. For much longer, they have been seen as fattening foods. Why do farmers feed their livestock on grains? To plump them up for market.

For half a century we have been told to avoid saturated fat, even though there is no good evidence that fat is inherently fattening. By diligently avoiding it, we have ended up replacing whole, unprocessed foods, such as red meat and butter, with starchy carbs of the highly refined and processed sort, often containing added sugar. Net result? We're getting fatter.

The problem with sugar, and starchy refined carbs, is that the surge of energy they give you is shortlived. Like newspaper ignited with a match, refined carbs burn up quickly, producing a sharp spike in blood sugar level that encourages our bodies to produce insulin, the fat storage hormone, so encouraging weight gain. Unlike protein and fat, which give a longer, slower, steadier release of energy, when our blood sugar level crashes after eating carbs, our appetite is unsatisfied and we crave more food.

This is probably what Paltrow means when she writes in her book: "Sometimes when my family is not eating pasta, bread or processed grains … we're left with that specific hunger that comes with avoiding carbs".

Fruit and vegetables are, of course, carbohydrates, and do contain natural sugar. However, they also contain micronutrients, notably fibre, that slow down the rate at which sugar is released in the blood. The same applies to whole, unrefined carbohydrates, such as brown rice. What's more, the general effort required to chew fruit, vegetables and whole grains puts a natural brake on how much we can eat. But it's easy to overeat refined carbs, the kind Paltrow avoids.

If the daily diet in the Paltrow household includes protein (fish/meat/eggs/pulses), unprocessed fats (butter/olive oil), plenty of vegetables and some fruit, then it is healthy, nutrient-rich and lacking in nothing. If that's what the Paltrow kids eat, she's doing them a favour.

Yes, children do have slightly different nutritional requirements from adults: they need more fat and protein. But filling their plates with empty calories in the form of white pasta, bread and rice is no nutritional kindness.

• Joanna Blythman is the author of What To Eat (Fourth Estate, £9.99). To order a copy for £7.99 with free UK p&p, go to guardianbookshop.co.uk.